Heat sealing apparatus for plastic bags

ABSTRACT

An improved plastic bag sealing apparatus comprised of an improved resilient planar heater formed of a heating wire embedded in a resilient silicon rubber material. The heater is shaped to conform to the flat planar surface of a T-bar shaped heating element, and clamped in place with insulators to provide maximum transfer of heat to a heating edge formed by the web portion of the T-bar. In an optional configuration the heater is in the form of a tubular rod seated in a channel in the T-bar directly above the heating edge for transferring maximum heat to the heating edge. In another optional embodiment, the tubular rod heater is a brass rod covered with intermediate insulating sleeves and spirally wound heating wire. In the latter embodiment the tubular rod heater is inserted in a passageway through T-bar shaped heating element and sealed with a potting compound. The containment of heat and transfer of maximum heat to the T-bar permits a substantial improvement in thermal efficiency and a substantial reduction of power consumption. The heating edge of the T-bar is covered with an easily replaceable heating channel coated with a non-stick, heat resistant material such as polytetraflouroethylene (TEFLON).

This application is a Continuation-In-Part of application Ser. No.09/358,152 filed Jul. 20, 1999, now U.S. Pat. No. 6,119,590, which is acontinuation of Ser. No. 09/087,752 filed May 29, 1998 now U.S. Pat. No.5,947,019.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a portable heat sealing apparatus for plasticbags and more particularly, relates to an improved more efficient heatsealing apparatus.

2. Background Information

Plastic bags are sealed by heating the perimeter at the opening to thebag. Heat is applied across the opening, under pressure that melts theplastic and “welds” the opening of the plastic bag. There are plasticbag heat sealers that include drawing a vacuuming then sealing theopening by applying heat to melt and weld the opening together. Thesedevices are complicated and expensive, and have jaws that are heated tomelt the plastic bag opening after a vacuum has been drawn in the bag.

There is also a plastic bag heater disclosed and described in U.S.patent application Ser. No. 100/319,174 issued Feb. 22, 1966 toHutchinson et al, one of whom is the inventor of the invention disclosedherein. This patent discloses a portable plastic bag sealer that has asealing edge with controlled heat to seal the plastic bag my applyingpressure against the opening of the plastic bag with the bag positionedon a surface. The device disclosed is simple in construction and use,and can be operated by one hand of an operator. It provides superiorseals to comparable portable apparatus that were previously available.

However this device is somewhat thermally inefficient and can have someexposed outer hot surfaces as are typically exposed in the use of hotcloth irons. The heater is in the form of a T-bar that is heated byceramic heating elements on either end. The heating elements mustgenerate a considerable amount of heat energy to heat the entire T-barto attain sufficient high temperature on the heating edge to seal theplastic bag. This results in the entire portable bag sealer becoming hotenough to degrade internal components and thus, shorten the sealersoperating life. In addition, the inefficient heater requires substantialpower to generate sufficient heat to seal a plastic bag.

It is therefore, one object of the present invention to provide animproved plastic bag sealer that provides more efficient heating of thesealing edge.

Yet another object of the present invention is to provide a plastic bagsealer having an improved heater that provides more uniform heat atlower power inputs.

Still another object of the present invention is to provide a plasticbag sealing apparatus, which reduces heat loss by preventing heattransfer to surrounding components and the surrounding atmosphere.

Still another object of the present invention is to provide a plasticbag sealing apparatus that allows small gauge insulation wire to be usedthat is less expensive and lasts longer when used at the reducedtemperatures.

Yet another object of the present invention is to provide an improvedplastic bag sealer having an improved heater that prevents transfer ofheat to external components (e.g., the cover) thereby providing a safersealer.

Yet another object of the present invention is to provide an improvedplastic bag sealing apparatus with an improved heater that preventsinsulating plastic parts from breaking down due to high operatingtemperatures.

Still another object of the present invention is to provide a plasticbag sealer having a silicon rubberized heater with embedded heater wiresthat are clamped in place by insulating plates alone or in conjunctionwith fiberglass insulation.

Still another object of the present invention is to provide a plasticbag sealing apparatus having an improved heater that provides greaterheat transfer to the T-bar edge, and less heat transferred to structuralcomponents.

Yet another object of the present invention is to provide a plastic bagsealing apparatus having an improved flat silicon sheet heater havingembedded heating wires that provide uniform heating over the entirelength and width of the T-bar heater.

Yet another object of the present invention is to provide an improvedplastic bag sealer having an improved heater utilizing thermallyinsulating standoffs that assists in reducing transfer of heat tosurrounding components and external surfaces.

Still another object of the present invention is to provide a plasticbag sealing apparatus having an improved tubular rod heater. Theimproved heater will deliver uniform heat energy concentrated in theimmediate area of the “T-bar”sealing edge. The rod heater design reducesthe required input heat and further reduces heat energy loss tosurrounding components and atmosphere.

Still another object of the present invention is to provide an improvedhand-held plastic bag sealer having improved long life elastic foamsupport springs for resiliently supporting an elongate T-shaped heater.

Yet another object of the present invention is to provide an improvedhand-held plastic bag sealer having integrally formed thermallyinsulating standoffs on a heater clamping plate.

BRIEF DESCRIPTION OF THE INVENTION

The purpose of the present invention is to provide an improved portableplastic bag sealing apparatus that is more efficient and user friendlythan the model disclosed in the above identified patent.

The plastic bag heat sealing apparatus of the present invention isconstructed of a T-shaped (i.e., T-bar) heating element providing asealing edge that is covered with a replaceable channel having anon-stick, heat resistant and durable plastic coating such aspolytetraflouroethylene (TEFLON). The TEFLON coating on the channel iseffective to prevent the sealing apparatus from sticking to the plasticmaterial. The top of the T-shaped heater is heated by an improved heatercomprised of resilient material having an integral heating wire. Theresilient heater covers the entire surface on the top of the T-barheating element, and is clamped in place with an insulator.

A pair of rails on either side of the heating edge of the T-bar areattached by means of springs that allow the heating edge to pass througha slot formed by the rails to heat a plastic bag positioned on anon-stick surface. The heating assembly is enclosed in a housing whichhas a centrally located handle used to press the heater down whensealing a plastic bag.

A thermostat is provided to vary the temperature of the hot sealing edgeapplied to the plastic bar. The thermostat allows continuous adjustingthe heat intensity according to the thickness of the plastic bags beingsealed. Three different settings are provided. The first setting is forplastic bags or films from one to two mils thick. The second setting isfor medium bags or films three to four mils thick. A third setting forthicker bags having plastic material that is six to ten mils thick isprovided.

The resilient heater is preferably a rectangular shape of soft siliconmaterial having a heating wire encapsulated in the material. The heatingwire is incorporated in the material in a winding path along one side,and winds back along the other side. This provides uniform and evenheating over the entire heater and high heat transfer to the T-barheating element. This results in more uniform heating and lower power toachieve temperatures that provide an efficient seal.

The resilient heating element is also clamped in place, on top of theT-bar heater, and cuts stray heat loss by as much as fifty percent (50%)substantially reducing input power. The reduction in heat transfer tothe surrounding components prevents cracking and damage to thecomponents due to mechanical shock loads during rough handling.

In an optional but preferred embodiment of the invention the rails fromeither side of the heating edge of the T-bar heater are attached byadvanced long life elastic foam support springs constructed of aurethane foam such as that known as PORON manufactured by RogersCorporation of Connecticut. The resilient elastic foam supports do nottake a compression set and therefore has a very long spring life.Further the stress loads on the hand held portable sealer are relativelylight. These foam springs are an improvement over the stainless steelleaf springs, which after many repetitions, can fail. The elastic foamsupport springs because of the light stress loads will have a nearlyinfinite life.

The system is also improved with an integrally formed heater clampingplate and standoffs. The integrally formed clamping plate and standoffsare of a heat resistant thermoplastic resin such as “FORTRON”manufactured by Hoechst Celanese Corporation. This material isparticularly suitable for use in electrical and electronic devices thatrequire high heat resistance. The thermoplastic clamping plate clampsthe heater in place on the T-bar heat sealing element.

In an optional embodiment a rod type heater is used that is lower incost and more directly heats the T-bar sealing edge of the plastic bagsealer. This heater is a cylindrical rod that seats in a channel orgroove in the T-bar heater directly above the heat sealing edge. Thecylindrical rod heater is specially designed heater or may be a heaterknown as a CALROD heater from General Electric Corporation or anequivalent. The cylindrical rod heater is clamped by a plate having acomplimentary groove or channel to securely hold the heater in place. Aninsulator is provided between the heater and clamping plate. Preferablya thermally conductive lubricant or grease is provided in the T-barchannel to maximize heat transfer to the heat sealing edge.

In another optional embodiment the rod heater is a specially designedheater inserted in a passageway in the T-bar. The specially designedheater is comprised of a brass rod covered by a fiberglass sleeve havinga nichrome wire spirally wound around it and than returning over asecond fiberglass sleeve. The assembly is then covered with a thirdfiberglass sleeve and then inserted lengthwise through a elongatepassageway through the T-bar. The passageway is then sealed with apotting compound that allows the transfer of heat to the sealing edge ofthe T-bar. This arrangement provides a less costly rod heater and a moreefficient transfer of heat to the sealing edge.

The above and other novel features of the invention will be more fullyunderstood from the following detailed description and the accompanyingdrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a isometric view of an improved plastic bag sealing apparatusaccording to the invention.

FIG. 2 is an exploded view of the heat sealing apparatus of FIG. 1.

FIG. 3 is an end view of resilient heater having an embedded heaterwire.

FIG. 4 is a sectional view of an improved resilient heater illustratingthe heating wire configuration.

FIG. 5 illustrates the plastic bag heat sealing apparatus positioned forsealing a plastic bag.

FIG. 6 illustrates the plastic bag heat sealing apparatus sealing aplastic bag.

FIG. 7 is an enlarged view illustrating operation of the plastic bagheat sealer taken at 7 of FIG. 6.

FIGS. 8a through 8 d illustrate the improved uniform heat transfer anduniform temperature profile of the new resilient silicone heater versusthe old single point isolated ceramic heaters.

FIG. 9 is an exploded view of an optional embodiment of the heat sealingapparatus of FIG. 1.

FIG. 10 is an exploded view illustrating an optional heaterconfiguration for heating the T-bar sealing edge.

FIG. 11 is a sectional view illustrating the optional heaterconfiguration of FIG. 10.

FIG. 12 is an end view similar to FIG. 5 illustrating the optionalheater configuration of the plastic bag sealing apparatus positioned forsealing a plastic bag.

FIGS. 13a through 13 i illustrate the construction of a rod heater foruse in the invention.

FIG. 13j illustrates the insertion of the specially constructed rodheater in the T-bar.

FIGS. 14 and 15 illustrate the final construction of the T-bar heaterwith a specially designed rod heater.

FIG. 16 is a sectional view showing the specially designed rod heatersealed inside the T-bar.

DETAILED DESCRIPTION OF THE INVENTION

A plastic bag sealer is shown in the isometric view of FIG. 1, and issimilar in design to the sealing apparatus disclosed and described inU.S. Pat. No. 3,236,174 issued Feb. 22, 1966 to Hutchinson et al. Theplastic bag sealer 10 has a handle 12 for one-hand operation in sealinga plastic bag 14 lying on a table 16, or other suitable surface whichincludes a pad or mat 18. The temperature of sealer 10 is controlled byknob 20 which controls a thermostat as will be described in greaterdetail hereinafter. The operator grasps plastic bag sealer 10 by handle12, and presses it down firmly against pad 18, on plastic bag 14. Asealing edge heats, melts thereby, seals the opening of plastic bag 14,as will be described in greater detail hereinafter.

The construction of plastic bag sealer 10 is shown in exploded view ofFIG. 2. Plastic bag sealer 10 has a handle 12 as previously described;and a housing or cover 24, covering a heating element 26, heater 28,thermostat 30 and insulators 32 and 34. Plastic bag sealer 10 isconnected to electrical power with cord 36. The construction andoperation of plastic bag sealer 10 substantially reduces powerconsumption and the transfer of heat to surrounding components, allowingsmaller gauge wires 38 and 40 to be used without the heavy insulationheretofore required. Heating element 26 is in the shape of a T-barhaving a flat upper surface 42, and a vertical centrally located web 44,providing a heating edge 46, covered by replaceable heating channel 48having a heat resistant, non-stick coating 49 of TEFLON(polytetraflouroethylene) (FIG. 7). Heating element 26 is heated byrubberized silicon heater 28, as will be described in greater detailhereinafter. Heating channel 48, covering heating edge 46, remains in anormal retracted position (FIG. 5) in housing or cover 24, between rails50 and 52, attached to upper surface 42 of heating element 26 by leafsprings 54 and 56.

Heater 28 is securely clamped, covering the entire planar surface byMicarta insulator 32, held in place by screws 33. An additionalfiberglass insulator 34 may be clamped between insulator 32 and heater28 if desired. The uniform construction and heating of heater 28 allowstransfer of almost all heat to heating element 26 and heating edge 48with heat loss and transfer to other components being minimized. Housingor cover is insulated from heating element by ligonite standoffs 25 ofimpregnated wood mounted by screws 27 below and screws 29 above. Thiskeeps cover 24 from any contact with heated surfaces.

The construction of heater 28 is shown in greater detail in FIGS. 3 and4. Heating element 28 is comprised of rubber or silicon sheets 58 and 60having a heating wire 62 embedded between the silicon rubberized sheets58 and 60.

The heater 28 is shown in FIG. 4 with upper silicon rubber sheet 58removed for clarity. Heating wire 62 traverses a circuitous path downand along one edge of rectangular silicon rubberized sheet 60 to theopposite end and then back to the other end and is connected to powercord 36 by wires 38 and 40. This arrangement provides uniform heatingover the entire length of heater 28. Slot 64 is provided to fit aroundthermostat 30, which controls the heat applied through knob 20.Thermostat 30 is preferably a short shaft model (MOD HP-84 orequivalent) bi-metal thermostat manufactured by Bimet Corporation ofMorris, N.J.

The application of the device, to seal a plastic bag, is illustrated inFIGS. 5 through 7. Plastic bag 14 is placed on a suitable pad or mat 18,on a flat surface such as a table 16. Plastic bag heat sealer 10 is thenplaced over plastic bag 14, near the opening 15 with rails 50 and 52resting on plastic bag 14 and heating element 26 retracted. With theappropriate amount of heat set by knob 20, plastic bag sealer 10 ispressed downward with handle 12 allowing TEFLON coated heating edge 48to compress bag 14, heating it until it melts and welds the plasticclosed as illustrated in FIG. 7. When handle 12 is released, leafsprings 54 and 56 retract heating edge 48 into housing 24 ready to sealthe next plastic bag. Another plastic bag 14 is then placed on mat 18,and the process is repeated. Each plastic bag can be sealed in just asecond or two. Thermostat 30 is adjusted continuously by knob 20 toaccommodate materials of different thicknesses. Preferably, threesettings are provided. A first setting is for thin bags or plastic filmsfrom one to two mils thick. A second setting, at a slightly highertemperature, is provided for bags and films from three to four milsthick. A third and highest setting is provided for thick bags and filmsfrom six to ten mils thick. The thinnest bags will seal in approximatelyone second, with the thicker bags in the range of three to ten milsthick, will seal in one and one-half to two seconds.

FIGS. 8a through 8 d are diagrams that illustrate the improvedperformance from the uniform heat transfer and uniform temperatureprofile of the resilient embedded heater versus the old type heaterusing single point ceramic heaters. FIGS. 8a through 8 bdiagrammatically illustrate the inefficient operation of the isolatedceramic heaters. Isolated ceramic heaters 66, spaced apart on T-bar 68,transfer heat to coated sealing edge 70 which when pressed down, producethe heating profile shown in FIG. 8b. Note, that the temperaturegradient varies substantially (i.e., approximately 50° F.) in the areasdirectly beneath ceramic heaters 66. Thus, considerable heat is neededto assure a seal along the entire width of the plastic bag.

In contrast, the improved plastic bag sealer provides a more efficienttransfer of heat to seal a plastic bag. Uniform resilient heater 72,securely clamped by insulating clamp 74, uniformly transfers heat toT-bar 76 and coated heating edge 78.

The improved portable plastic bag sealer with the uniform resilientheater produces the heating profile shown in FIG. 8d. The resilientheater produces a uniform heat transfer and uniform temperature gradientthat varies less than about 15° F. beneath the entire sealing edge 78.Since the heat transfer is relatively uniform over the area beingsealed, lower heat power can be used, a more uniform seal is producedand the plastic bag sealer has less heat transfer to external surfacesmaking it safer.

A modified preferred embodiment of the plastic bag sealer is shown in anexploded view of FIG. 9 where like parts are indicated by like referencenumbers throughout. The plastic bag sealer has handle 12, as previouslydescribed, housing or cover 24, covering heating element 26, heater 28and thermostat 30 as before. Insulators described previously 32, 34 andstandoffs 25 are replaced by an integrally formed clamping andinsulating plate 35 have an integrally formed standoffs 37, 37′constructed preferably of a thermoplastic resin such as FORTRONmanufactured by Hoechst Celanese Corporation or an equivalent. Thisthermoplastic resin clamping plate securely clamps heater 28 on top ofheating element 42 and efficiently insulate cover 24 and handle 12 fromheat. Clamping plate 35 is securely clamped on the upper flat surface ofT-bar heating element 42 by screws 39 and attached to cover 24 by screws29.

While stainless steel leaf springs 54 and 56 provide an efficientresilient mounting for rails 50 and 52 they are subject to fatigue andsometimes fail after long use. Therefore an improved mounting for rails50 and 52 has been provided as shown in FIG. 9. Leaf springs 54 and 56are replaced with long life resilient elastic foam supports 154 and 156constructed of urethane foam such as PORON manufactured by RogersCorporation of Connecticut, supporting L-shaped rails 150 and 152 byplates 158 and 160. Plate 160 is riveted to rails 150 and 152 whileplates 158 are fastened to each end of heating element 26 by screws 162and insulator 164. Elastic foam support 154 and mounting hardware isthen concealed by insulating covers 168 preferably constructed from anABS (acrylonitrile-butadiene-styrene) thermally insulating plastic.

The plastic bag sealer functions as before. A plastic bag, 14 is placedon a pad 18 and heat sealer pressed down on the bag using handle 12.Urethane resilient elastic foam supports 154 and 156 at each end ofrails 150 and 152 act as springs allowing edge 48 to press down and meltthe plastic, welding the plastic edges together. The advantage of theurethane elastic foam support is that it does not take a compressionset. It generally will have a much longer life than the stainless steelleaf springs of the first embodiment. Further since the stress loads arerelatively light they will last almost indefinitely.

While the resilient planar heater of the previously described inventionis more efficient than previous designs to transfer heat to the edge ofthe T-bar flange, a disadvantage is that it transfers substantial heatto the entire T-bar. It is also somewhat expensive to produce becausethe heater is embedded in a flexible planar material. Anotheradvantageous design is the provision of a heater that can transfer moreheat directly to the heating edge of the T-bar heater rather than to theentire T-bar. For that purpose an optional heater configuration has beendesigned.

An optional improved heater design is illustrated in FIGS. 10 through12. In this design the flexible planar heater is replaced by a tubularrod heater 80 known as a CALROD heater of General Electric Corporationor an equivalent. The CALROD heater is a tubular metal design having aheating wire passing through the center which is packed with anelectrically insulating and thermally conductive material. Heater 80 iscomprised of a metal tube 82 having a heating element 84 traversing thelength of the tube with electrical connections 86 and 88 at each end.Electrical connector 86 will connect to cord 36 (FIG. 9) whileelectrical connector 88 will connect to thermostat 30 for temperaturecontrol as before. Generally heating element 84 is embedded in athermally conductive and electrically insulating material to conductheat to metal tube 82.

To maximize transfer of heat from rod heater 80 to heating edge 90 ofT-bar heater 92, a lengthwise groove or channel 94 is provided forreceiving tubular rod heater 80. Clamping plate 96 constructed of a PPS(polyphenylene sulfite) synthetic material, such as FORTRON,manufactured by Hoechst Celanese Corporation that has a complementarygroove or channel 98 to securely clamp rod heater 80 in channel 94 anddirect most heat energy to heating edge 90 of the T-bar as indicated bythe arrow in FIG. 11.

Tubular heater 80 is assembled in T-bar 92 by placing the tubular rod inchannel 94. Preferably a thermally conductive lubricant 102 is firstplaced in channel 94. PPS clamping plate 96 is then securely clamped ontop of tubular heater 80. This construction and configuration serves totransfer maximum amount of heat energy to sealing edge 90 of T-barheater 92. In the configurations shown tubular heater 80 is securelyclamped in arcuate channels or grooves 94 and 98 between clamping plate96 and T-bar heater 92. In yet another embodiment of the invention aspecially designed rod heater was conceived to improve the efficiencyand reduce the cost of the heating device. This specially designedrod-heater is illustrated in FIGS. 13a through 13 i. Specially designedrod heater 170 (FIG. 13j) is comprised of a cylindrical brass supportrod 172 covered with a No. 8 fiberglass mesh 174 as shown in FIG. 3b.Support rod 172 is preferably brass but can be fabricated from metal(i.e., brass, aluminum or steel) or ceramics (i.e., Pyrex glass,fiberglass, etc.). Fiberglass mesh sleeve 174 is stretched to coverbrass rod 172. A nichrome heater wire 176 is then spirally wound overfiberglass sleeve 174 and brass rod 172. A second No. 8 fiberglass meshtubing 178 is then slid over and covers nichrome heater wire 176, firstfiberglass mesh tubing 174, and brass rod 172.

A second nichrome heater wire 180 is then spirally wound in a reversedirection covering second fiberglass mesh tubing 178 first nichromeheater wire 176, first fiberglass mesh tubing 174, and brass rod 172. Athird No. 6 fiberglass mesh tubing 182 is then slid over the assembly ofthe nichrome wires 176 and 180, fiberglass mesh tubing 174 and 178 andbrass rod 172. To complete the assembly, nichrome wires 176 and 180 arejoined at the end 184 by soldering or twisting them together and thefree ends are then connected by wires 186 to a power supply (not shown).

Nichrome heater wire 176 and 180 can be 34 AWG gauge (0.006″), 32 AWGgauge (0.008″) or 30 AWG gauge (0.010″) and is wound on support rod in acoil normally between the range of 10 to 30 turns per inch. The totalnichrome wire coil resistance is from 100 ohms to 200 ohms.

Specially designed rod heater 170 is then inserted in T-bar 190 having alengthwise passageway 192 in T-bar 190 constructed to receive thespecially designed rod heater. The assembly is then completed asillustrated in FIGS. 14 through 16. To complete the assembly, passageway192 through T-bar 190 is then filled with a potting compound 196 from anozzle 198 to secure rod heater 170 in passageway 192 in T-bar 190.Planar surface 200 of T-bar 190 is then covered with an insulatingmaterial 194.

Potting material compound or material 196 should preferably be a heatconductive material to enhance the transfer of heat from rod heater 170to heating edge 202 of T-bar 190. Also nichrome wires 176 and 180 couldbe a continuous wire wound spirally down around first fiberglass tubing174 then reversed to spirally wind around second fiberglass tubing 178.Insulator 194 assists in directing heat from rod heater 170 inpassageway 192 in T-bar 190 to heating edge 202. Thus the structure asdisclosed provides a novel specially designed rod heater 170 completelyenclosed in passageway 192 in T-bar 190 providing substantial transferof heat to heating edge 202.

The optional configuration for heating described operates in the samemanner previously described, and is shown in FIG. 12. Heating edge 90 iscovered with a replaceable TEFLON coating 48 as before and positionedbetween rails 150 and 152 (FIG. 9) above a plastic bag 14 that is to besealed. Plastic bag 14 is placed on a smooth surface 16 preferablyhaving a heat insulating pad 18. To seal plastic bag 14 a downward forceon handle 12 presses heated edge 90 of T-bar heater 92 against the openend of plastic bag sealed 14 melting the plastic to “weld”it together.

Thus, there has been described a plastic bag sealers, with substantialimprovements over the plastic bag sealer disclosed and described in theU.S. Pat. No. 3,236,174 referred to hereinabove. The plastic bag sealeris provided with a soft silicon heater comprised of a heating wireembedded in the silicon rubber. In an optional embodiment stainlesssteel leaf springs are replaced with urethane elastic foam supports thatact like springs but provide a longer life. The resilient urethane foamsupport acts similar to a spring and have a nearly indefinite lifebecause of the light loads applied to the plastic bag sealer. In anotheroptional embodiment a rod heater is positioned in a arcuate channel inthe T-bar heating element directly above the heating edge to maximumtransfer of heat energy. The tubular rod heater is clamped in acomplementary grooves between the T-bar heater and a thermallyinsulating clamping plate. Heating temperatures and transfer of heatenergy to surrounding components is substantially reduced. A reductionof up to fifty percent (50%) in power consumption to achieve the sameheating temperature is achieved. The sealing edge channel is preferablyTEFLON coated, and is easily replaced on the heating element. Animproved sealing edge and reduction in sticking of the material can beprovided by occasionally wiping the edge of the aluminum sealing channelwith a rag impregnated with silicon oil. The plastic bag sealer quicklyand easily seals plastic bags placed on a back-up mat, providing a goodseal with limited shrinkage.

This invention is not to be limited by the embodiment shown in thedrawings and described in the description which is given by way ofexample and not of limitation, but only in accordance with the scope ofthe appended claims.

What is claimed is:
 1. A heat sealing apparatus for plastic materialscomprising; a T-shaped heating element having an upper planar surfaceand a flange perpendicular to the planar portion forming a heating edge;a tubular rod heater in intimate contact with said T-shaped heatingelement; said tubular rod heater comprising; a brass rod; a heating wirespirally wound around said brass rod; an insulator insulating saidheating wire from said brass rod; an outer insulating sleeve coveringsaid heating wire and said brass rod; said tubular rod heater positionedin contact with said T-shaped heating element to maximize heat transferto said heating end; a housing covering said T-shaped heating elementand said tubular rod heater; a handle on said housing for pressing saidheating apparatus downward against a surface; a pair of rails mounted oneither side of said heating edge forming a slot through which saidheating edge may pass; biasing springs for biasing said rail over andbeyond the end of said heating edge to maintain said heating edge in aretracted position until ready to use; a connector connecting saidresilient heater to electrical power to heat said heating element andheating edge; whereby when said heat sealing apparatus is presseddownward on a plastic material placed on a surface, said heating edgepasses through said slot between said rails and heats and seals saidplastic material.
 2. The apparatus according to claim 1 in which saidbiasing springs are resilient elastic foam springs constructed ofpermanent set heat resistant urethane foam.
 3. The apparatus accordingto claim 2 including a replaceable heating sealing channel mounted overand covering said heating edge of said T-shaped heating element.
 4. Theapparatus according to claim 3 wherein said replaceable heat sealingchannel is coated with a heat resistant non-stick coating.
 5. Theapparatus according to claim 3 in which said heat resistant, non-stickcoating is polytetraflouroethylene.
 6. The apparatus according to claim1 including a lengthwise groove formed in said T-shaped heating element;said tubular rod heater being seated in said groove.
 7. The apparatusaccording to claim 6 including a clamp for firmly clamping said tubularrod heater in said groove.
 8. The apparatus according to claim 7 inwhich said clamp has a complementary groove identical with and fittingover said lengthwise groove in said T-shaped heating element.
 9. Theapparatus according to claim 8 in which said clamp is constructed of aninsulating material.
 10. The apparatus according to claim 9 including aheat conductive coating in said lengthwise groove to maximize heattransfer to a heating edge on said T-shaped heating element.
 11. Theapparatus according to claim 1 in which said T-shaped heating elementhas a lengthwise passageway; said tubular rod heater being inserted insaid lengthwise passageway.
 12. The apparatus according to claim 11including a heat conductive insulating seal filling said lengthwisepassageway to seal said tubular rod heater inside said T-shaped heatingelement.
 13. The apparatus according to claim 12 in which said heatconductive insulating seal comprises a potting compound filling saidlengthwise passageway to seal said passageway around said tubular rodheater.
 14. The apparatus according to claim 11 in which said tubularrod heater comprises; a first insulating sleeve stretched over saidbrass rod; a first heating wire spirally wound over said firstinsulating sleeve from a first end to a second end; a second insulatingsleeve stretched over said first heating wire and said first insulatingsleeve; a second heating wire wound in a reverse spiral from said secondend to said first end; said first and second heating wire being joinedat said second end; said outer insulating sleeve stretched over to coverand insulate said brass rod, first and second heating wires andintermediate insulating sleeve.
 15. The apparatus according to claim 14in which heating wires are nichrome wires.